Over the-past decade, tissue engineering has evolved from a loose collection of different disciplines to a biotechnology field in its own right. A combination of chemical engineering and cell biology, with input from genetics, surgery and other disciplines, tissue engineering combines living cells, biological and synthetic materials into implants that can function in the human body. Researchers have taken the first steps toward creating semisynthetic, living organs such as livers, hearts, and pancreases by culturing colonies of living hepatocytes, cardiomyocytes, and islet cells, respectively.
An endoluminal procedure is a medical procedure which takes place in one of the many hollow spaces, or lumens, within the human body. These procedures may take place, for example, in vascular, gastrointestinal (GI), or air exchange lumens, among others, and they may involve disease diagnosis and/or treatment. Millions of endoluminal procedures are performed each year in hospitals around the world. Endoluminal procedures are often performed utilizing devices such as endoscopes and catheters.
Researchers introduced microencapsulation of engineered tissue in the late 1970's. Microcapsules are easy to produce and have been used in the delivery of everything from agricultural chemicals, cosmetics and fragrances to pharmaceuticals and medicines. The use of microencapsulated engineered tissue has been generally confined to providing immuno-isolation for tissue implants that either produce a therapeutic substance (e.g., the use of pancreatic islet cells for producing insulin), or which perform a metabolic function (e.g., the use of hepatocytes for plasma detoxification). Fabricators of microcapsules commonly aim for a membrane pore size that will allow diffusion of molecules of molecular weight up to 50,000 daltons. Such pore sizes generally are small enough to block invasion by immune cells and most immune molecules, but are large enough to allow the inflow of nutrients and oxygen and the outflow of cellular byproducts. Encapsulation of this form is generally meant to be permanent, lasting for the lifetime of the encapsulated tissue and/or the length of therapy required.